1. Field of the Invention
This invention pertains generally to pipe scanners for the non-destructive examination of piping and, more particularly, to such scanners that can continuously scan the 360° circumference of a pipe over an extended length.
2. Description of Related Art
A leak in the Alaskan oil pipeline caused a major environmental concern that necessitated the shutdown of the Alaskan oil pipeline for a considerable period. As a result, a scanner was developed to continuously monitor the condition of the pipeline to avoid a similar catastrophe in the future. The scanner developed for the Alaskan Pipeline was designed for a 34 inch (86.36 cm.) diameter pipe and only would scan the lower half of the pipe. Typically, pipe scanners are limited to a 24 inch (60.96 cm.) stroke, i.e., the distance they can travel along a pipe without human intervention. After completing a 24 inch (60.96 cm.) stroke they would need to be manually relocated on the pipe to the next 24 inch (60.96 cm.) interval. That interval is even less when compensating for overlap to guarantee 100% coverage. The design of the Alaskan Pipeline scanner was a good first step to avoid future environmental contamination, however, a more versatile design is desired that can scan the 360° circumference of the pipe over an extended length without human intervention. Desirably, such a scanner should be capable of traveling axially along the pipe at relatively high speeds without a need for relocation except when negotiating a riser or vertical support member, which in the case of the Alaskan Pipeline are approximately 60 feet apart.